I am getting conflicting information on the dates of older carrier units. We just did a large commercial building with 24 80,000 BTU furnaces in the individual suites. Can somebody give me a little help in dating them, here are two examples:
Q1A46849 I think this is 1991?
R1A58163 I think this is 1981?
X1A01921 I think this is 1971?
Thank you in advance for any help you can provide here.
Sherlock Homes Inspection & Appraisal, LLC